Infrared study of a La0.7Sr0.3MnO3-delta micrometric transistor channel

We studied the polaron conductivity in a field-effect transistor (FET) based on the doped oxide La0.7Sr0.3MnO3-delta, where the electric field penetration depth is enhanced due to suppression of metallic conduction by large oxygen deficiency delta, by mid-infrared microspectroscopy (wavelengths from 1.4 to 12 mu m) on a 3 mu m wide active channel. Synchrotron radiation was used to obtain the mid-infrared response at the diffraction limit. We found that bound polarons, although clearly detected, play a minor role in the electric field-induced dc conductivity modulation, which may be then attributed to the accumulation/depletion of free carriers. (c) 2007 Elsevier B.V. All rights reserved.